Antenna efficiency is especially important for satellite communications, where signals from distant satellite transponders can be weak. The more noise a satellite antenna introduces to a signal, the larger the dish antenna that should be used with the antenna. Further, in communications systems that both transmit and receive, interference from the transmit signal may reduce the sensitivity of the communications system to the receive signal or may burn out components of the system such as low noise amplifiers.
To reduce noise and to provide isolation between signals, satellite communications systems typically use a horn-type feed antenna with an orthomode transducer (“OMT”). While horn-type feed antennas and OMTs can provide satisfactory performance, specialized OMTs increase the complexity and cost of the feed system. Antennas for satellite communications are also typically fixed, and the antenna beam must be physically adjusted by moving the antenna structure to compensate for errors in positioning. Moreover, horn-type feeds are machined parts that must be attached to a printed circuit board containing other common functions in satellite communications systems, causing the size of the system to be large in size and costly to manufacture.